Various types of 3D scanners are available, each more suited to specific applications, e.g. for scanning small objects with high resolution or for scanning large objects with low resolution. To scan all around an object requires that either the object is moved past the scanner, e.g. on a turntable, or the scanner moved around the object.
Several types of known scanners are capable of capturing complete surface information of objects and scenes. Generally, these scanners can be separated into three categories: namely photogrammetric scanners, fixed station laser scanners and hand-held 3D shape scanners. The scanners generate data points or other structures representing the scene or object scanned and this data can be post-processed by software to allow visualisation and to generate 3D representations or 3D computer models of the scene or object.
Photogrammetric systems reconstruct a 3D scene or object based on analysis of multiple overlapping 2D images. Provided common features are visible and identified in the images and camera calibration parameters are known or determined, it is possible to extract 3D metric scene or object information. In some cases, the cameras are pre-calibrated. In other cases, self-calibration is attempted based on the image matches.
Fixed station scanners scan a scene from a fixed location. Typically, fixed station scanners are arranged to scan a modulated laser beam in two dimensions and acquire range information by measuring the phase-shift of the reflected modulated laser light or the time-of-flight of a reflected laser pulse. By panning the scanner through 360°, it is possible to produce a 360° panoramic range map of the scene. To scan a complete scene often requires moving the fixed station scanner to a number of different scanning locations. Depending on the size of scene, scanning time is typically 10-30 minutes. Some fixed station scanners also comprise a digital camera that is arranged to capture colour information for each surface point in the scan of the scene so that dual colour and range images can be generated. Other fixed station scanners incorporate multiple lasers to allow acquisition of colour as well as range information.
Hand-held 3D shape scanners comprise a hand-held mobile scanner-head that is commonly maneuvered by a user about the object being scanned. Typically, the scanner-head includes a range sensor for determining the local shape of the object by sensing the position in space of the surface points of the object relative to the scanner-head. For example, the range sensor may sense the position in space of the surface points via laser triangulation. The hand-held 3D shape scanners also comprise a position and orientation system that measures the position and orientation of the mobile scanner-head in space during the scan. The local shape information is then coupled with the scanner-head position and orientation information to enable a 3D computer model of the object to be constructed.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.
It is an object of the present invention to provide a flexible and portable 3D scene scanner that is capable of scanning wide-area scenes, or to provide a position and orientation system that is capable of sensing the pose of a mobile object in 6D, or to at least provide the public with a useful choice.